Method for securing a mounting bar at one end of a printing blanket and resulting printing blanket

ABSTRACT

A method for securing a mounting bar at one end of a blanket including a lithographic layer and a support layer and, interposed between those two layers, at least one reinforcing woven layer. The end of the blanket, where the bar is to be fixed, is stripped until the main or single reinforcement of the blanket is exposed and the bar is fixed at least on the stripped part on the end of the blanket. The invention is applicable to printing machines.

FIELD OF THE INVENTION

The invention relates to a process for securing a mounting bar to oneend of a printing blanket which has a lithographic layer and acompressible layer, and at least one woven reinforcing layer between thelithographic layer and the compressible layer, and the invention relatesto a blanket thus obtained.

BACKGROUND

The blankets of the prior art, as described in the document EP 0 742760, for example, are gripped at both ends in a mounting bar that bearson the free surfaces of the two exterior layers.

It is known that the mechanical performance of the mounting bars is ofprime importance in printing machines. In effect, loss of the bar bypossible unseating of it can have very serious consequences, withpossible breaking of the printing cylinders and loss of production forthe user.

SUMMARY OF THE INVENTION

The present invention proposes a process for securing a mounting bar toa blanket that increases the mechanical performance of the mounting barsand eliminates the above-mentioned risk.

In order to attain this aim, in the process according to the invention,the end of the blanket on which a mounting bar is to be secured isstripped until the main reinforcement or sole reinforcement of theblanket is free, and the mounting bar is secured to the reinforcement.

According to one characteristic of the invention, the mounting bar issecured to the reinforcement by gluing.

According to one characteristic of the invention, both surfaces of thebeam are stripped, and the mounting bar is secured by gluing to the twoexposed surfaces of the beam.

A printing blanket according to the invention has at least one surfaceof the reinforcement stripped, and the mounting bar is secured by gluingto this surface.

According to another characteristic of the invention, the mounting barhas the shape of a flat strip.

According to yet another characteristic of the invention, the mountingbar has an L-shaped profile wherein one limb is glued onto the exposedbeam portion.

According to yet another characteristic of the invention, the mountingbar has a U-shaped profile wherein one limb is glued on one exposedsurface of a beam.

According to yet another characteristic of the invention, the twosurfaces of the beam are stripped, and each limb of the mounting bar isglued on one of the two exposed surfaces of the beam.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood, and other aims,characteristics, details and advantages of it will appear more clearlyin the following explanatory description with reference to the appendedschematic drawings, given only as an example illustrating an embodimentof the invention, and in which:

FIG. 1 is an oblique view of an end of a blanket according to theinvention;

FIGS. 2 and 3 illustrate two blanket structures that are particularlysuitable for application of the invention; and

FIGS. 4 to 6 are diagrammatic views illustrating three steps of theprocess according to the invention.

DETAILED DESCRIPTION

FIG. 1 shows one end of blanket 1 onto which mounting bar 2 is mountedby gluing, the bar having a general U shape in which end 3 of theblanket is engaged. This blanket in FIG. 1 has three layers, namelyexterior lithographic layer 5, exterior base layer 6, and, insertedbetween these two layers, reinforcing layer 7 which comprises a main orsole reinforcement, such as beam 8. In the part of end 3 of the blanketthat is taken between the two limbs of rod 2, layer 6 is removed at 9 inorder to expose beam 8, as will be described in detail further on. Theglue indicated at 4 and which is used as a means of securing themounting bar to end 3 of the blanket is arranged directly on the beam inzone 9. Thus, a part of upper limb 11 of the mounting bar is secured, bymeans of a layer of glue, at its front part to the exterior surface andat its end part to the beam 8, while the other limb 13 of the mountingbar is secured to the exterior surface of lithographic layer 5.

Blanket 1 represented in FIG. 2 could in reality have a structure suchas is illustrated in FIG. 2 or FIG. 3. In the example of FIG. 2, betweenlithographic layer 5 and opposite exterior layer 6, which is a slightlycompressible polymer layer, the blanket has stabilizing fabric layer 15,compressible layer 16 into which beam 8 is integrated, and compactpolymer layer 17, the beam being arranged inside layer 16 on the layer17 side. The blanket according to FIG. 3 is distinguished from theblanket represented in FIG. 2 by the fact that compact polymer layer 17has been eliminated. Consequently, the blanket of FIG. 3 can have asmaller thickness of 1.1 mm in comparison with the 1.2 mm of the blanketaccording to FIG. 2. Of course, the invention applies also to blanketsof standard thickness, generally between 1.35 and 2.35 mm.

FIGS. 2 and 3 show the blanket after beam 8 has been stripped at part 9,the original contour of end 3 being represented by a broken line.

FIGS. 4 to 6 show three steps of the process for mounting of bar 2 ontoend 3 of blanket 1. In a first steps, represented in FIG. 4, a part ofthe thickness of the blanket is delaminated over an appropriate width inorder to expose the wires which provide the stretch resistance of theblanket, that is to say, in general the aramid beam 8. Advantageously,the exposed surface as well as the rest of the surface which is to beglued can be prepared for gluing or for molding by washing with solventsor by mechanical brushing or the equivalent. Then, in a secondoperation, the beam thus exposed is coated with glue as illustrated inFIG. 5. After spreading the glue, one proceeds to mount bar 2 on end 3of the blanket. FIG. 6 shows the mounting bar in its position before theeffective gluing. Then, by application of a force in the direction ofarrow F, limb 11 of the bar is forced towards the exterior surface tothe position shown in FIG. 1. After hardening of the glue, a high degreeof resistance to pull-out is obtained, which is necessary for mountingthe blanket on an offset printing cylinder.

As an example, the blanket can be stripped for a distance of, forexample, 1 to 20 mm, and the blanket can be grasped by mounting barswith a length, width or depth of between 5 and 30 mm.

It should be noted that a number of modifications can be made to theembodiment described and represented. Thus, the blanket can be strippedon both surfaces simultaneously until freeing of the wires which providethe stretch resistance of the blanket. It is also possible to use asimple bar, for example, a bar in the form of a flat rod or a bar withan L-shaped profile, which will then be secured to the exposed,glue-covered surface of the strengthening wires. As a variant, the barcan be molded onto the stripped blanket. The bar can be made of metalbut also of composite material, of thermoplastic reinforced, or not, byfibers or by a metallic mesh.

The invention can be used for blankets with a single reinforcement,blankets with two lithographic layers, blankets with a polymer backing,and blankets with thinned ends, as described, for example, in thedocument FR 9900828.

The above-mentioned single reinforcement can consist of an aramid beam,a beam produced with other fibers with a high modulus and high strength,a known fabric with different weaves, or else a mesh or a plastic film.

The invention also applies to a blanket of more conventional design andwhich, if necessary, has more than one reinforcement in its body.

1. A process for securing a mounting bar to one end of a printingblanket which includes a lithographic layer, a base layer, and, insertedbetween the lithographic and base layers, at least one woven reinforcinglayer, the process including stripping an end of the blanket onto whicha mounting bar is to be secured, until a reinforcement of the blanket isexposed, and securing the mounting bar at least on an exposed part ofthe reinforcement.
 2. The process according to claim 1, includingspreading glue on at least the exposed part of the reinforcement andgluing the reinforcement to the bar.
 3. The process according to claim2, including exposing two opposite surfaces of the reinforcement, andgluing the mounting bar to the two exposed surfaces of thereinforcement.
 4. The process according to claim 1, including moldingthe mounting bar onto the blanket after exposing the reinforcement.
 5. Aprinting blanket obtained according to the process of claim 1, in whichat least one surface of the reinforcement is exposed, and the mountingbar is glued to the surface of the reinforcement.
 6. The blanketaccording to claim 5, wherein the mounting bar is a flat rod.
 7. Theblanket according to claim 5, wherein the mounting bar has an L-shapedprofile and one limb of the mounting bar is glued to the exposed surfaceof the reinforcement.
 8. The blanket according to claim 5, wherein themounting bar has a U-shaped profile, wherein one limb of the mountingbar is glued to one exposed surface of the reinforcement.
 9. The blanketaccording to claim 8, wherein two surfaces of the reinforcement areexposed, and each limb of the mounting bar is glued to a respective oneof the two surfaces of the reinforcement.
 10. The blanket according toclaim 5, wherein the mounting bar is molded to the blanket.